由于想在macOS上安装"wget"命令，但需要先安装brew工具，安装brew工具需要安装xcode，但macOS 10.15.2 默认没有安装xcode，安装了xcode【Version 11.4.1 (11E503a)】之后，通过brew官网的教程给的指令来安装brew：
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"执行后报错：
xcode-select: error: invalid developer directory '/Library/Developer/CommandLineTools'Failed during: /usr/bin/sudo /usr/bin/xcode-select --switch /Library/Developer/CommandLineTools
从报错来看，/Library/Developer/CommandLineTools的确不存在，通过：
xcode-select -p
以找到正确的路径，于是稍微修改一下官方给的指令：
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh | sed 's#/Library/Developer/CommandLineTools#$(xcode-select -p)#')"于可以看到正确的结果：
Already up-to-date.==> Installation successful!==> Homebrew has enabled anonymous aggregate formulae and cask analytics.Read the analytics documentation (and how to opt-out) here:https://docs.brew.sh/AnalyticsNo analytics data has been sent yet (or will be during this `install` run).==> Homebrew is run entirely by unpaid volunteers. Please consider donating:https://github.com/Homebrew/brew#donations==> Next steps:- Run `brew help` to get started- Further documentation:https://docs.brew.sh
接着按照官方教程安心安装wget命令啦：
$ brew install wget
Continue reading 关于mac系统上brew的安装.
